Shoulder arthroplasty implant system

ABSTRACT

An implant for shoulder arthroplasty includes a stem and optionally a head component or a cup component. The stem is sized and shaped to fit into an intramedullary canal of the humerus. The proximal portion of the stem has a concave taper and the distal portion of the stem has a taper. The distal taper includes an anterior-posterior taper and a medial-lateral taper. The shape of the stem loads the metaphysis of the humerus with a greater load than the load applied to the diaphysis of the humerus.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 16/208,324, filed Dec. 3, 2018, which application is acontinuation of U.S. patent application No. 15/445,658, filed Feb. 28.2017, now U.S. Pat. No. 10,172,714, which claims the benefit of U.S.Provisional Patent Application No. 62/300,853, filed Feb. 28, 2016; theentire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

Shoulder replacement surgeries were first performed in the 1950's in theUnited States to treat severe shoulder fractures. Over the years, theimplants used in shoulder replacement surgeries have been improved toprovide better outcomes and to expand the clinical indications for useto include shoulder arthroplasty for degenerative conditions. Modernshoulder replacement implants are generally of two designs; anatomic andreverse.

The anatomic shoulder implants are intended to restore the naturalkinematics of the shoulder by replacing the humeral head and glenoidwith similarly shaped prosthetic designs that recreate normal anatomy.The anatomic shoulder implant often has a spherical humeral head and ashallow concave glenoid that articulates with the spherical head. Afterthe intact humeral head is resected, the anatomic shoulder implants havea stem configured to be securely placed down the shaft of the humerusand the spherical head is often fixed to the stem via a mechanical taperpress fit. The glenoid prosthetic component, usually made from a polymersuch as ultra-high molecular weight polyethylene (UHMWPE) is eithercemented directly into the remaining intact glenoid or affixed to ametallic tray, which is secured to the native glenoid bone using bonescrews, cement, or similar attachment methods.

The reverse shoulder is different from the anatomic shoulder implants inthat the spherical surface is placed on the remaining intact glenoid andthe concave articular surface is placed on the humerus. The reverseshoulder also has a stem configured to be securely placed down the shaftof the humerus. The polymer concave articular surface is fixed to thestem using a mechanical lock. The spherical head, in the reverseshoulder, is fixed to the remaining intact glenoid using a base plate.

Anatomic shoulder implants are used in patients to treat a variety ofdiseases that affect the shoulder joint and cause pain. A majority ofthese patients have osteoarthritis where the normal load bearingarticular cartilage has eroded away. Reverse shoulders are generallyused in patients with a weak, irreparably torn or insufficient rotatorcuff. The rotator cuff is the anatomical term used to describe the groupof muscles and their tendons around the shoulder joint that stabilizesthe shoulder for proper motion of the joint. The reverse shoulderimplants alter the kinematics of the joint and substitute for thefunction of the dysfunctional rotator cuff so that other muscles likethe deltoid muscle can be used to lift the arm. Reverse shoulderimplants may also be used in other severe cases, such as in cases ofsevere glenoid bone loss, where additional stability is required.

In cases where an anatomic arthroplasty has failed, it is sometimesappropriate to revise the anatomic arthroplasty to a reversearthroplasty. To address this situation, a few shoulder arthroplastysystems have been introduced into the market that are “convertible” froman anatomic configuration to a reverse configuration. The main advantageof these convertible designs is that they obviate the removal of theexisting anatomic humeral stem. Removal of the stem is technicallydifficult, associated with longer operative times, increased blood loss,and higher complication rates. Most designs are convertible by using anadaptor tray that allows the spherical head component of the failedanatomic arthroplasty to be exchanged with the adaptor tray whichsupports the concave humeral component of the reverse arthroplasty.These adaptor trays are also called “onlay” designs as the reverse polycup is on top of the resection plane.

The adaptor trays used in these onlay designs are not always idealbecause they add thickness in the joint that is potentially undesirable.This added thickness can create “over-tensioning” of the joint thatover-tensions the soft tissue around the joint. Over-tensioning thejoint can lead to decreased range of motion and also can cause acromialfractures, which are difficult to treat. Nonetheless, these are not theonly complications that that can arise with current shoulder implants.

Another preventable complication that can occur in shoulder arthroplastyis bone loss due to stress shielding. Press-fit stem designs whichachieve fixation in one region of the humerus may preferentially shieldanother area. The proximal metadiaphyseal and metaphyseal stressshielding are caused by stems which achieve secure fixation distally inthe diaphysis. This may lead to a decrease in the physiologic loads inthe proximal aspect of the humerus. Without this load, bone loss in thisarea can occur and potentially lead to eventual loosening of theimplant. In addition, revising a failed arthroplasty that has resultedin significant proximal humeral bone loss is very difficult. There isincreased fragility of the bone making fracture much more likely. Often,these fractures involve the bony attachments of the rotator cuff tendonswhich often compromises shoulder function. Stem designs that have agenerally cylindrical shape are particularly problematic because theyrequire a large number of sizes to address varying patient anatomy.Anatomically, the humeral head is not centered on the shaft (diaphysis)of the humerus. The stem designs that achieve fixation in the shaftmust, by necessity, have multiple humeral head options with “offset” inorder to recreate normal anatomy. As a result these stem designs alsorequire a large inventory of different sizes and offsets to recreate thenormal anatomy.

Current stems can also require more bone removal than is desired by thesurgeon. Bone sparing designs may allow a greater amount of native boneto be preserved. For all of the above reasons, some new stem designshave the potential to be an improvement over existing stems.

Therefore, there is a need for improved shoulder arthroplasty devicesand methods of use. At least some of the challenges described herein areaddressed by the embodiments disclosed below.

SUMMARY OF INVENTION

The present application generally relates to medical devices, systems,and methods of use. More preferably, the present application relates toimplants and systems used in surgical procedures, such as in a shoulderarthroplasty.

A shoulder arthroplasty implant system and method of use are disclosedbut this is not intended to be limiting, and other uses arecontemplated. The system is convertible between an anatomicconfiguration and a reverse shoulder configuration with an inlay design(i.e., no intermediate tray is required to switch between anatomic andreverse configurations, which may lead to less over-tensioning of thejoint). The stem has been designed to primarily load the metaphysis inorder to maximize bone compaction, reproduce a more physiologic load tothe proximal humerus, thereby preventing stress shielding and loosening.An optimal shape and size of the system has been derived by astatistical model that reduces the number of sizes required to fit thepatient population, and wherein each size may fit its portion of thepopulation more closely. Additionally, the shape of the stem is designedto allow for the stems to be used in both left and right shoulders.Insertion of the stem into a prepared bone creates compaction of thebone adding to the stability of the implant.

In a first aspect, an implant for shoulder arthroplasty comprises a stemhaving a proximal portion, a distal portion, an anterior portion, aposterior portion, a medial portion, and a lateral portion. The stem hasa size and shape for insertion into an intramedullary canal of a humerusbone. The humerus has a metaphysis and a diaphysis. The proximal portionof the stem comprises a concave taper decreasing in size in a directionextending from the proximal portion toward the distal portion, and thedistal portion comprises a distal taper decreasing in size in adirection extending from the proximal portion toward the distal portion.The distal taper comprises a taper in a direction extending between theanterior portion and the posterior portion, and also the distal tapercomprises a taper in a direction extending between the medial portionand the lateral portion. The shape of the stem is configured to load themetaphysis with a load greater than a load on the diaphysis.

The implant may further comprise a lateral fin, an anterior fin, and aposterior fin. The lateral fin may extend radially outward from thelateral portion of the stem. The anterior fin may extend radiallyoutward from the anterior portion of the stem. The posterior fin mayextend radially outward from the posterior portion of the stem. Thelateral, anterior, and posterior fins may be configured to engagecancellous bone in the metaphysis or epiphysis to provide rotationalstability to the stem. A lateral surface of the distal taper maycomprise a convex curve extending in a direction from the proximalportion toward the distal portion, and a medial surface of the distaltaper may comprise a concave curve extending in a direction from theproximal portion toward the distal portion. The taper in the directionextending between the anterior portion and the posterior portion may besymmetric about a medial plane of the implant so as to allow bilateralusage in the shoulder. The taper in the direction extending between theanterior portion and the posterior portion has a width which may be maybe substantially equal to a diameter at a distal end of the concavetaper on the proximal portion of the stem.

The implant may comprise a cylindrical extrusion disposed adjacent theproximal portion of the stem. A first point may be disposed on ananterior portion of cylindrical extrusion and a second point may bedisposed on a posterior portion of the cylindrical extrusion. A thirdpoint may be disposed distally away from the first point and the thirdpoint may be disposed on an anterior portion of the distal taper. Afourth point may be disposed distally away from the second point and thefourth point may be disposed on a posterior portion of the distal taper.The first, second, third, and fourth points may define a first totalincluded angle of a proximal portion of the distal taper. A fifth pointmay be disposed at a distal end of the stem and may be disposed on theanterior portion of the stem. A sixth point may be disposed at thedistal end of the stem and may be disposed on the posterior portion ofstem. The third, fourth, fifth, and sixth points may define a secondtotal included angle of a distal portion of the distal taper. The secondtotal included angle may be less than the first total included angle.

A distal portion of the stem may comprise an hourglass shapedcross-section with a width extending in a direction from the anteriorportion toward the posterior portion that may be greater than a width atthe medial portion or a width at the lateral portion. A distal portionof the stem may comprise a cutout section extending through the stem ina direction from the anterior portion toward the posterior portion, andthe cutout may comprise medial and lateral edges which are offset from amedial surface and a lateral surface of the stem. The cutout may beconfigured to carry bone graft material.

The proximal portion of the stem may comprise a rim that comprises oneor more protrusions extending outward therefrom, and the one or moreprotrusions may be configured to be received into a correspondingreceptacle in an articular cup or a head component. The implant mayfurther comprise a collar element disposed circumferentially around theproximal portion of the stem. The implant may also comprise one or morefenestrations disposed in the proximal portion of the stem. The one ormore fenestrations may extend in a direction from the proximal portiontoward the distal portion, and the one or more fenestrations may besized to allow a surgical instrument to pass therethrough.

The implant may further comprise a tapered receptacle disposed in theproximal portion of the stem that is configured to receive a cooperatingtapered protrusion disposed on an articular cup or disposed on a headcomponent. The tapered protrusion may have a length that is sized topermit use in an anatomic or reverse arthroplasty, and the taperedprotrusion may extend through the tapered receptacle thereby permittingan anatomic head component to be used with the stem. The implant mayfurther comprise a coating that is disposed over at least a portion ofthe stem. The coating may be configured to promote bone ingrowth intothe stem. The stem may be a single piece.

A system for shoulder arthroplasty may comprise any of the implantsdescribed herein and an articular cup coupled to the stem, or a headcomponent coupled to the stem. The articular cup may be coupled directlyto the stem without requiring an intermediate engaging element such as atray. An apex of the cup may be disposed distally of a resection planein the humerus.

In another aspect, a stemless implant for shoulder surgery comprises abody having a proximal portion, distal portion, and an outer surface. Acylindrical extrusion is substantially perpendicular to and adjacent theproximal portion of the body, and at least a portion of the outersurface is configured to contact bone. The outer bone contacting surfacecomprises a concave taper.

The concave taper may be defined by at least one radius revolved arounda central axis of the cylindrical extrusion. The implant may furthercomprise a first fin extending radially outward from the bone contactingsurface. The first fin may be configured to provide rotational stabilityand tapering from the proximal portion toward the distal portion. Thefirst fin may have a width adjacent the proximal portion that is greaterthan a width adjacent the distal portion. The implant may furthercomprise a second, third, and fourth fin. The first fin may be disposedon a lateral portion of the implant, the second fin may be disposed on amedial portion of the implant, the third fin may be disposed on ananterior portion of the implant, and the fourth fin may be disposed on aposterior portion of the implant.

The cylindrical extrusion may comprise one or more protrusions extendingoutward therefrom, and the one or more protrusion may be configured tobe received into a corresponding receptacle in an articular cup or ahead component. The implant may further comprise a collar elementdisposed circumferentially around a proximal portion of the cylindricalextrusion. The implant may also comprise one or more fenestrationsdisposed in the proximal portion of the body. The one or morefenestrations may extend in a direction from the proximal portion towardthe distal portion, and the one or more fenestrations may be sized toallow a surgical instrument to pass therethrough.

A system for shoulder arthroplasty may comprise any of the implantsdescribed herein and an articular cup coupled to the body or a headcomponent coupled to the body. The articular cup may be coupled directlyto the body without requiring any intermediate engagement element suchas a tray. An apex of the cup may be disposed below a resection plane ina humerus bone.

In another aspect, a method for performing either anatomic or reverseshoulder arthroplasty on a shoulder having a humerus bone, comprisesperforming a proximal humeral osteotomy on the humerus, removingproximal bone from the humerus, and inserting an implant into thehumerus and fixing the implant thereto. The implant loads metaphysis ofthe humerus, and the implant also loads the diaphysis of the humerus.The metaphysis load is greater than the diaphysis load.

The implant may comprise a stem having a proximal portion with a concavetaper and a distal portion with distal taper.

inserting the implant may comprise inserting the stem into the humeruswithout contact between the distal portion and cortical bone of thehumerus. The implant may be stemless. The method may further comprisecoupling an articular cup or a head component to the implant. Theimplant may comprise a stem and coupling the articular cup to theimplant may comprise coupling the articular cup directly to the stem. Anapex of the cup may be disposed below a resection plane in the humerus.Inserting the implant may comprise engaging one or more fins on theimplant with the humerus. The implant may comprise a collar element thatis disposed adjacent a proximal portion of the implant, and insertingthe implant comprises advancing the collar element toward a proximalportion of the humerus. The stem may comprise one or more fenestrationsdisposed in the proximal potion of the stem, and the method may furthercomprise passing a surgical instrument through the one or morefenestrations.

These and other embodiments are described in further detail in thefollowing description related to the appended drawing figures.

INCORPORATION BY REFERENCE

All publications, patents, and patent applications mentioned in thisspecification are herein incorporated by reference to the same extent asif each individual publication, patent, or patent application wasspecifically and individually indicated to be incorporated by reference.

BRIEF DESCRIPTION OF THE DRAWINGS

The details of one or more variations of the subject matter describedherein are set forth in the accompanying drawings and the descriptionbelow. Other features and advantages of the subject matter describedherein will be apparent from the description and drawings, and from theclaims.

FIG. 1 shows a perspective view of the shoulder arthroplasty system in areverse configuration.

FIG. 2 shows a frontal view of the system with a cup in a reverseconfiguration.

FIG. 3 shows a perspective view showing of the stem with headun-installed

FIG. 4 shows a perspective view of the stem and cup.

FIG. 5 shows an anterior cross-section of the stem installed in ahumerus.

FIG. 6 shows a frontal view of the stem component.

FIG. 7 shows a frontal view of the details of the proximal portion ofthe stem

FIG. 8 shows details of the proximal portion of the stem in bone.

FIG. 9 shows a frontal cross-section of the stem and cup.

FIG. 10 shows a cross-section of the stem and cup assembled.

FIG. 11 shows a medial view of the stem component.

FIG. 12 shows a frontal view of the stem component

FIG. 13 shows a frontal view of the stem component and lateral findetails.

FIG. 14A shows a cross-section of the stem component. FIG. 14B shows adetailed cross-section of the lateral fin.

FIG. 15A shows a lateral view of the stem component. FIG. 15B shows afrontal view of an alternate anterior/posterior fin geometry. FIG. 15Cshows a perspective view of the same embodiment.

FIG. 16A shows a frontal view of the stein. FIG. 16B shows the distalcross-section of the stem.

FIG. 17A shows a medial view of an alternate embodiment of the medialsurface geometry.

FIG. 18 shows a lateral view of an alternate embodiment of the lateralfin.

FIG. 19 shows a perspective view of the preferred bone growth coatingplacement.

FIG. 20A shows a frontal view of alternate stem geometry with a cutoutfor additional bone graft placement. FIG. 20B shows the same embodimentin a perspective view.

FIG. 21 shows a frontal view of a stemless configuration.

FIG. 22A shows a cross section of an alternate embodiment of the stemcomponent with protrusions. FIG. 22B shows a perspective view of thesame embodiment.

FIG. 23 shows a cross-section of the head.

FIG. 24A shows a frontal view of an alternative embodiment of the stemwith a collar. FIG. 24B shows a cross-section of the same embodiment.

FIG. 25A shows an auxiliary view taken normal to the proximal end of thestem of an alternative embodiment of the stem with fenestrations forimplant removal. FIG. 25B shows a perspective view of the sameembodiment.

FIG. 26 shows an alternate bone growth coating placement.

FIG. 27A, 27B, 27C, 27D shows the method of determining the center ofthe resection plane using a disk and pin.

FIG. 28A, 28B, 28C, 28D, 28E, 28F show the reaming procedure to createthe proximal bone cavity.

FIG. 29 shows a cross-section of the broach in the humerus.

FIG. 30A shows a cross-section of the stemless broach in the humerus.FIG. 30B shows a frontal view of the stemless broach.

DETAILED DESCRIPTION OF THE INVENTION

Before the present subject matter is further described, it is to beunderstood that this subject matter described herein is not limited toparticular embodiments described, as such may of course vary. It is alsoto be understood that the terminology used herein is for the purpose ofdescribing particular embodiments only, and is not intended to belimiting. Unless defined otherwise, all technical terms used herein havethe same meaning as commonly understood by one skilled in the art towhich this subject matter belongs.

Disclosed is a shoulder arthroplasty system that is optionallyconvertible in use between an anatomic and a reverse shoulderimplantation configuration. The system includes a short stem prosthesisthat may provide several advantages. In the reverse shoulderconfiguration, the system includes an articular surface cup arranged inan inlay configuration on a receptacle of the stem. This may provide fora much more compactly sized system with respect to an onlayconfiguration. The system is configured to preferably achieve fixationin the metaphysis to preferably provide rotational and axial stability.The shoulder arthroplasty system may be implanted in both a press fitand a cemented configuration.

The system can be implanted using an installation technique thatpreferably removes as little bone as possible thereby conserving bone inthe patient. It is designed on anatomy preferably based on a statisticalshape model matching that of the humerus, as described in detail below.It should be appreciated that a statistical shape model is just anexample, of a non-limiting means of analysis and that other means ofanalysis are within the scope of this disclosure.

FIG. 1 shows a perspective view of the shoulder arthroplasty system in areverse configuration. The system includes a stem component 1 and apolymer cup 2 in a reverse configuration. FIG. 2 shows a frontal view ofthe system with the aforementioned stem component 1 that is sized andshaped to be inserted into the humerus. The stem has a monoblock ormonolithic configuration that is a single piece structure. The singlepiece stem reduces manufacturing costs and hospital inventoryrequirements compared to a modular stem design. The cup 2 has an angledprofile that provides a greater range of motion with less potential fornotching which is loss of bone where the implant comes in contact withthe glenoid, possibly during some movements. One of skill in the artwill appreciate that the stem or stemless embodiments may be used with,or without, or in combination with, any of the other features describedin this specification (e.g. fins, fenestrations, tapers, etc.).

The cup component 2 defines a curved articulating surface near to theresection plane. This provides minimal lateralization andinferiorization for a convertible prosthesis, which leads to a moreanatomical reconstruction. The cup component 2 is interchangeable withthe stem 1. A collection of multiple cup components 2 can be used for asingle, corresponding stem component wherein each cup component of thecollection has a particular articulating surface diameter and offset.This permits a user to select a cup component for use having a desiredsurface diameter.

FIG. 3 shows a perspective view of the shoulder arthroplasty system witha head component 3 uninstalled from the stem 1. The stem component 1also includes a mechanical taper 5 that serves as a securing mechanismfor the head component 3 and when secured to the stem 1. The anatomichead component 3 provides an articular surface 6 for anatomic shoulderreconstruction.

FIG. 4 provides perspective views of the stem component 1. As describedin detail below the stem has an anatomic shape that is configuredpursuant to a statistical shape model. It should be appreciated that astatistical shape model is just an example, of a non-limiting means ofanalysis and that other means of analysis are within the scope of thisdisclosure. For example, other means of analysis including anatomicanalysis, geometric analysis, anthropometric analysis, mechanicalanalysis, and kinematic analysis are within the scope of thisdisclosure. In this embodiment, the stem has three fin like protrusions,a lateral fin 51, anterior fin 52, and the posterior fin 53 configuredto cut into cancellous bone in the metaphysis to provide rotationalstability when the system is implanted in bone. The fins are configuredto enhance rotational stability of the stem while avoiding corticalcontact in the metaphysis. The anterior and posterior fins 52 and 53 maybe used interchangeably when the stem is used in a left or right side ofthe patient.

In FIG. 5, a cross section of the stem component inserted into thehumerus is shown. The proximal end 7 of the stem 1 is positioned along aresection plane 8, which is the area exposed in surgery when the humeralhead is surgically removed prior to preparation and implantation. Anaxis 90 normal to the resection plane 8 is at an obtuse angle 91 fromthe long axis of the bone 9.

FIG. 6 shows a frontal view of the stem component. The stem has anoverall taper shape such that the implant generally increases in sizeproximally which improves wedged fixation. This configuration preservesbone by providing minimal removal of bone, especially in the greatertuberosity and humeral metaphysis. The design allows the stem to becentered proximally within the resection plane, which thereby allows thespherical head component of the anatomic configuration to be alsocentered on the resection plane, recreating normal anatomy. The outerbone contacting surfaces of the stem are configured to optimize theproximal bone loading in the proximal metaphysis of the humerus andreduce loading distally in the diaphysis. The taper shape has a proximalconcave taper 10 that is generally conical and a distal taper 11 that istapered in both the medial-lateral direction as well as theanterior-posterior direction. Additional details about the proximal anddistal tapers are described elsewhere in this specification.

The stem has a proximal end 7, distal end 12, lateral side 13 and medialside 14. The proximal portion of the stem has a short cylindricalextrusion 15 perpendicular to the proximal end 7. In the preferredembodiment the cylindrical extrusion 15 is 2.7 mm and may range from 2.5mm to 3 mm. While this is a preferred embodiment, the stem design mayhave other dimensions and. would work without the cylindrical sectionwhere the proximal portion of the stem is conical right up to theproximal end 7. The design with the cylindrical extrusion 15 ispreferred because this truncates the conical taper such that thediameter of the proximal end 7 is reduced for the same taper. In apreferred embodiment the diameter of the cylindrical extrusion rangesfrom 30 to 40 mm although other dimensions are possible. The diameterincreases with increasing patient anatomy.

FIG. 7 shows details of the concave taper 10 in the proximal portion ofthe stem. Distal to the cylindrical extrusion 15 the stem geometrytransitions to a concave taper 10. The proximal end 16 of the concavetaper 10 is congruent to the distal end of the cylindrical extrusion 15and extends to a distal end of the taper 17. The concave taper 10 isdefined by at least one radius 18 revolved around the axis 19 throughthe center of the cylindrical extrusion 15. The center of the radius 20used to create the concavity is outside the cone created by therevolution of the straight line 21 created between proximal end 16 andthe distal end 17 of the concave taper 10. In the preferred embodimentthe length of the conical section from the proximal end 7 to the distalend 17 may be 18 mm but other lengths are possible. In alternateembodiments, the length of the conical section could range from 12-30mm. The diameter of the proximal end of the concave taper 10 ispreferably equal to the cylindrical extrusion 15 described above. Thediameter of the distal end of the taper 17 in the preferred embodimentmay be 9 mm and could range from 7 to 11 mm, although other sizes arealso possible.

FIG. 8 shows the concave taper 10 and the interaction with the proximalbone during insertion of the stem 1. The concave taper 10 is designed tocompact bone in the metaphysis during insertion. The compaction of boneis achieved when the stem is inserted into the bone. As the stemadvances distally in the humerus, bone is displaced along the concavetaper 10. The concave taper 10 is an advantageous shape because theangle formed between the axis 19 and a tangent line 22 to the concavesurface increases as the stem is advanced in the bone. This providesever-increasing compaction until final placement of the stem 1 isachieved.

In the configuration shown in FIG. 9, the cup component 2 is uncoupledfrom the receptacle 4 of the stem 1. The cup component attachesprimarily via a locking ring 27, but secondarily (and especially underload) with the taper 5. The proximal portion 23 of the stem houses thereceptacle for the anatomic head for anatomic shoulder replacement andthe articular cup 2 for reverse shoulder replacement. In the preferredembodiment, the stem has two receptacles; a female taper 5 and acylindrical cavity 24. The cylindrical cavity 24 is concentric to thecylindrical extrusion 15. The cylindrical cavity 24 starts at theproximal end 7 of the stem and extends distally to flat surface 25parallel to the proximal end 7. In the preferred embodiment, thecylindrical cavity 24 is 3.5 mm deep but it may be other depths. Betweenthe proximal end 7 and the flat surface 25 an annular groove 26 isformed to receive the locking ring 27 of the articular cup 2. A maleprotrusion 33 has a taper that corresponds to the taper 5 in the femalereceptacle so that the two components engage one another.

FIG. 9 shows a cross section of the stem component 1 and articular cup2. The female taper 5 is a conical tapered cavity that extends from theflat surface 25 of the cylindrical cavity 24 to a distal end 28. In theexample shown, the axis of the female taper 29 is congruent with theaxis of the cylindrical cavity 30. However, this embodiment is notlimited to this and the axis may be offset from the cylindrical cavity30 but preferably remains parallel to this axis. The female taper 5 isconfigured such that the diameter at the flat surface 25 is greater thanthe diameter at the distal end 28. The total included angle 31 of thefemale taper in a preferred embodiment is 4.6 degrees and the length is12 mm, although other dimensions are possible. The female taper 5 in thestem receives a conical protrusion 32 in the anatomic head 3 and theconical protrusion 33 in the articular cup 2. When pressed together, thefemale taper 5 and the conical protrusion 33 become fixed to one anotherwith an interference fit.

FIG. 10 shows a cross-section of the stem component 1 and articular cup2 in an “inlay” configuration. The articular cup 2 is affixed to thestem by the locking ring 27 in the annular groove 26 and interferencefit between the conical protrusion 33 and the female taper 5. In thepreferred embodiment, the apex 122 of the concave articular surface 6 isdistal to the proximal end 7 that sits flush to the resection plane 8.The inlay design greatly reduces the likelihood of over-tensioning thejoint. Sufficient bearing thickness is maintained to support the loadsand wear from patient activity.

FIG. 11 shows a medial view of the stem without the articular cup 2 oranatomic head 3. The distal taper 11 has an anterior surface 36 and aposterior surface 37. In the preferred embodiment the distal taper 11 issymmetric about a plane 38 that is congruent with the axis 19 of thecylindrical extrusion. The distal taper 11 is generally tapered in boththe medial-lateral direction and the anterior-posterior direction. Thedistal taper 11 has a medial-lateral width defined by the distance fromthe medial surface 34 to the lateral surface 35. The medial-lateralwidth decreases distally to create the medial-lateral taper. The distaltaper 11 has an anterior-posterior width defined by the distance fromthe anterior surface 36 to the posterior surface 37. Theanterior-posterior width decreases distally to create theanterior-posterior taper of the stem. The stem has a relatively thincross-section. In the anterior to posterior direction, the thincross-section is best described by the distal anterior-posterior width47. The thin cross-section accommodates offset of the humeral headrelative to intramedullary canal. This eliminates the need for left andright specific implants and further reduces inventory requirements. Inthe medial to lateral direction, the configuration is still thin enoughto allow rotations to match resection cut without contacting corticalbone. In addition, the short length allows further flexibility in thelocation of the implant proximally (angular and position) as the distalstem is not constrained by cortical bone during implantation. It alsopreserves bone by eliminating the need to ream cortical bone.

With reference to FIG. 11, the anterior-posterior taper of the distaltaper 11 is configured to reduce loading of the cortical bone in thediaphysis and create wedge fixation. The anterior-posterior taper issymmetric about the medial plane 38 of the implant. The anterior-postedor width 47 at the distal end is less than the proximal width 48. In thepreferred embodiment, the distal end of the distal taper is rounded inboth the medial-lateral and anterior-posterior directions. In thepreferred embodiment, the anterior-posterior width 47 at the distal endis 3.5 mm and the medial-lateral width at the distal end is 8, althoughother widths are possible

FIG. 12 shows details of the medial-lateral taper geometry of the stemin a frontal view. The medial lateral taper geometry is configured toconform to but not contact the medial and lateral cortex of the humerus.The taper geometry may provide rotational stability of the implant. Themedial-lateral taper is curved such that the distal end 49 of the stem 1is offset laterally a distance 39 from a point intersecting the axis ofthe cylindrical extrusion and the proximal end 7. In the preferredembodiment, this lateral offset is 8.7 mm for the median size and rangesfrom 7-13 mm, although other distances are possible. The lateral surface35 of the distal taper is defined by a convex curve 40 that extends fromthe proximal end to the distal end 49. The curve starts at a medialoffset 41 from the most lateral edge 42 of the proximal end 7 andextends to farthest lateral edge of the distal portion 43. The medialoffset 41 of the lateral surface 35 is the distance from the lateraledge of the cylindrical extrusion 42 to the proximal end of the lateralsurface 44. The offset 41 provides space for a lateral fin likeprotrusion that is described in detail below. The curve of the lateralsurface 35 is comprised of at least one radius. The medial surface 36 ofthe distal taper 11 is defined by a concave curve 45 that extends fromthe proximal end 7 to the distal end 49. The curve 45 starts at themedial most edge 46 of the proximal end 7 and extends to the farthestmedial edge 92 of the distal end. It should be noted that the taperedsection along the medial edge may also be interpreted as a fin-likeprotrusion and is described in further detail below. The medial curve 45is comprised of at least one radius. The medial-lateral taper increasesin width to the distal end of the cylindrical extrusion 15. The curvedmedial surface is sized and shaped to reduce fracture risk by spreadingimplantation forces over a larger area during implantation. The totallength of the implant from the center of the proximal end 7 to thedistal tip ranges from 44 mm to 48 mm although other lengths arepossible. The overall length of the implant from the most distal point49 to the farthest point superior point 50 ranges from 55 mm to 61 mmalthough other lengths are possible.

FIG. 13 shows details of the lateral fin 51. The lateral fin is definedby a lateral edge 54 that follows a convex curve from the lateral mostedge 42 of the cylindrical extrusion 15 to a point 55 that is tangent tothe lateral surface 35 of the distal taper 11. The convex curve can bedefined by at least one radius.

The cross-section of the lateral fin protrusion 51, shown in FIGS.14A-14B, is substantially triangular in the preferred embodiment. Theapex 56 of the triangular cross-section is congruent with the lateraledge 54 previously defined. Alternate embodiments, may includerectangular or hemispherical like cross-sections.

FIG. 15 shows a lateral view of the stem component. The anterior andposterior fins 52, 53 extend from a point 57 on the distal taper 11 thatis distal to the concave taper 10 and proximal to the distal end 12 ofthe stem. The anterior and posterior fins 52, 53 extend from the point57 to meet the cylindrical extrusion 15. In the preferred embodiment,the anterior and posterior fins 52, 53 are concave at the distal end ofthe fin 58 and convex at proximal end of the fin 59. The concave portionof the fin is tangent to the anterior/posterior surface 60 of the distaltaper 11 at the distal end of the fin 58. The convex portion of the finis tangent to the cylindrical extrusion 15 at the proximal end of thefin 59. FIG. 15B and FIG. 15C show an alternate embodiment of theanterior and posterior fins 52,53. In the alternate embodiment theanterior and posterior fins have a medial surface 109 and a lateralsurface 110. The medial surface 109 and lateral surface 110 aresubstantially parallel to each other, in additional fin geometries theanterior and posterior fins may be located closer to the lateral side 13than the medial side 14.

FIG. 16B, shows in the preferred embodiment, the part of the stem 1distal to the anterior and posterior fins of the stem has an hourglasslike cross-section. The cross-section is shaped such thatanterior-posterior width 61 at the medial and lateral sides is greaterthan the center 62 of the cross-section. This preserves bone whilekeeping any bone contacting surfaces at the medial and lateral edgeswith sufficient contact area to support implant loads and avoidcompromising the internal cortex.

FIG. 17A shows an alternate embodiment of the anterior-posterior tapergeometry of the taper. This embodiment provides a larger bone-contactingsurface on the medial and lateral surfaces and increases the wedgefixation in the metaphysis of the bone. The distal taper, in thealternate embodiment, has an anterior posterior width at the proximalend defined by the distance between an anterior point 63 on thecylindrical extrusion 15 and a posterior point 64 on the cylindricalextrusion 15. At a distance 65 distally along the distal taper 11, theanterior-posterior taper is further defined by a second width defined bythe distance between an anterior point 66 and a posterior point 67.These 4 points define a total included angle 68 of the proximal portionof the distal taper 11. A distal total included angle can be defined bythe second width, the distance between points 66 and 67 and the anterior69 and posterior 70 points at the distal end 12 of the stem 1. The totalincluded angle 71 of the distal portion of the distal taper is less thanthe proximal total included angle 68. FIG. 17B shows a similar geometrybut on the lateral fin 51. The lateral fin 51 has anterior and posteriorsurfaces 106 that form an angle 107. The angle 107 is greater than theangle formed by the distal taper angle 108

In a preferred embodiment, FIG. 19, the proximal bone contactingsurfaces 72 have a coating 73 for additional boney in-growth. Coatingsmay include plasma spray titanium, hydroxyapatite or similar coatingsknown in the art to enhance bone growth. In the preferred embodiment,the proximal 19-21 mm of the stem is coated. However, additionalembodiments could include coating the entire stem or any sections. FIG.26 shows one such embodiment of the placement of the bone growth surfacewhere only the fins 51, 52, 53 of the stem are coated with a bone growthcoating 73. The proximal section of the stem is grit blasted and thedistal portion is polished smooth.

FIG. 20A and 20B shows an alternative embodiment of the distal portionof the stem that has a cutout 74 to contain additional bone graft. Themedial 75 and lateral 76 edges of the cutout 74 is offset from themedial 34 and lateral surfaces 35 of the stem and extends through thestem 1 in the anterior-posterior direction. In this embodiment, theproximal extent of the cutout 74 is distal to the concave taper 10. Thecutout may be used in any stem embodiment described herein.

FIG. 21 shows an alternate embodiment of the stem, which does not have adistal taper as described in previous embodiments. This configuration iscommonly called a “stemless” or “canal sparing” implant. The device issurgically implanted in the same manner as the longer, “stemmed”,design, and therefore provides the surgeon with an additional optionwithout adding complexity. Stemless designs can be used to furtherenhance positional flexibility proximally when metaphyseal fixation isadequate and cementation is not required. In the stemless design, likethe “stemmed” design, the outer bone-contacting surface of the stem hasa concave taper 10. The stemless design, like the stemmed design, has acylindrical extrusion 15 perpendicular to the proximal end 7. Theconcave surface is defined by at least one radius that revolves aroundthe axis 19 created by the cylindrical extrusion 15. The stemless designalso includes at least one fin-like protrusion for rotational stability.As previously described, the fin-like protrusions extend from the distalportion of the stem to meet the proximal cylindrical section. The finstaper from the distal end 77 to a greater width at the proximal end ofthe fin 78. In a preferred embodiment, fins are located at the lateral79, medial 80, anterior 81 and posterior 82 aspects of the implant.

FIG. 22A shows a cross-sectional view of an alternate embodiment of theproximal end where the stem 1 has at least one protrusion 83 on the rim84 of the proximal end 7 to prevent rotation of the articular cup 2. Apreferred arrangement is four protrusions distributed evenly along therim 84 of the proximal end 7. The protrusion 83 extends from proximalend 7 of the stem. A rim 84 is created by the outer diameter of thecylindrical extrusion 15 and the cylindrical cavity 24. FIG. 23A showsthe protrusion extends radially from the inner surface 85 created by thecylindrical cavity 24 to the outer surface of the cylindrical extrusion15. However, alternative embodiments could include the protrusion onlyextending part of the way from the cylindrical cavity 24 to thecylindrical extrusion 15. The articular cup 2 for a reverse shoulderwould have mating indents 86, shown in FIG. 22B to receive theprotrusions 83. Any embodiment disclosed herein may include some or allof these features.

FIG. 23 shows a cross-sectional side view of the anatomic head component3 which may be used with any of the stem embodiments described herein.The anatomic head component 3 includes a long taper 32 that couples tothe corresponding taper in the stem to secure the anatomic headcomponent 3 to the stem. The longer than usual taper (relative tocurrently-existing systems) allows for a single interface for bothanatomic and reverse arthroplasty. Moreover, the long taper 32 extendsthrough the receptacle in the stem and is sized to allow the anatomichead component to be used in the same stem as an inlay articular cup (asdescribed above) without an intermediate tray. The anatomic headcomponent 3 includes a curved, anatomically accurate center and radiuscurvature of the articular surface 86 that closely matches normalanatomy of the humeral head. The head component 3 includes cutout 87 toreduce the weight of the component. The cutout 87 is disposed betweenthe outer rim of the head 88 and the central tapered protrusion 32. Arounded periphery 89 provides an atraumatic surface when in contact withsoft tissue.

FIG. 24A shows a frontal view of an alternative embodiment where thestem has a collar 95 on the cylindrical portion 15 of the stem 1. Thisembodiment is also known as a “collared” stem and is used with thesmallest stem sizes to allow for placement of the head or cup, dependingon whether an anatomic or a reverse is being implanted, it is allows theuse of the head or cup in a stem that is too small to accommodate themas the larger stems do. The collar 95 has a proximal surface 96, distalsurface 97 and radial surface 98. The proximal surface 96 of the collar95 is congruent to the proximal end 7 of the stem. The distal surface 97of the collar sits on the resection plane of the humerus. The radialsurface 98 has a diameter greater than that of the cylindrical extrusion15. The mating articular cup 2 component, shown in FIG. 24B, has anouter diameter 99 that is equal to the diameter of the radial surface98.

FIG. 25A and 25B shows an alternative embodiment of the stem withfenestrations. The fenestrations are used to insert instruments if theprosthesis needs to be removed. During revision, removal may be madedifficult by bone that has grown onto the stem. The fenestrations extendfrom the proximal end 7 distally. In the embodiment shown in FIG. 23there are four fenestrations. The first fenestration 100 is locatedbetween the lateral fin 51 and the posterior fin 53. A secondfenestration 101 is located between the lateral fin 51 and the anteriorfin 52. A third fenestration is located between the posterior fin andthe medial surface 34. The fourth fenestration 103 is located betweenthe anterior fin and the medial surface. Alternative embodiments mayinclude a different number of fenestrations.

The method to insert the stem is described below. In a first step, theproximal humeral osteotomy 111 is made through the anatomic neck of thehumerus. Reference FIG. 27A-27D. The osteotomy can be made using a saw,osteotome or equivalent bone cutting instrument. The osteotomy 111 is aplanar cut made at an angle to the long axis 9 of the bone. Theosteotomy can be sized using a set of sizing disks 112 and a guide pin113 placed through the center of the disk 114 to establish the osteotomycenter point 115. The set of sizing disks 112 include a matching diskfor each implant size. The guide pin 113 also acts as a temporaryfixation pin to help hold the disk 112. The disk is a flat cylinder usedto visualize the diameter of the proximal portion of the stem relativeto the resected bone surface created by the osteotomy 111. At least twoslots 116 are cut into the sizing disk 112 to help visualize the extentof the resected bone surface and thereby preventing oversizing of theimplant.

FIG. 28A-28F shows the next step being removal of the proximal bone. Theproximal bone of the humerus is removed to accommodate the proximalportion of the final implant, The bone is removed using a proximalreamer 117 that may be attached to handle for manual reaming by hand ora power drill. The humerus is reamed such that the cavity 118 created bythe reamer 117 is smaller than the final implant. FIG. 28E shows a crosssection of the reamer 117 in the humerus. FIG. 28F shows the reamerover-laid with the outline of the concave taper. The area between theconcave taper and the reamer is the volume of bone that will becompacted during the insertion of the stem.

The following step, shown in FIG. 29, shows a broach 119 that isutilized to compact the bone in the epiphysis and to create space forfinal implantation of the stem. The stemless broach 119 is designed tominimize bone cutting and improve bone compaction. The broach 119 alsoserves as the trial for the stem component disclosed herein. The broachmay also include slots to visualize the extent of the resected bonerelative to broach.

FIG. 30A shows an alternative embodiment of the broach where a stemlessbroach 105 may be used to clear bone proximally. The stemless broach 105may be inserted over the guide pin 113 to ensure the bone cavity for thestem is located at the osteotomy center point 115. The stemless broach105, shown also in FIG. 30B, may be used in both ‘stemmed’ implants andstemless implants. In the process of placing the broach, the metaphysealbone is compacted, thus achieving additional stability. The stability ofthe implant is then confirmed. Cementing may optionally be considered ifthe implant is not satisfactorily stable such as in patients withextremely poor bone quality. Once the glenoid is prepared, the finalstem component is fitted with a humeral head or the reversed cup and thejoint reduced.

While this specification contains many specifics, these should not beconstrued as limitations on the scope of an invention that is claimed orof what may be claimed, but rather as descriptions of features specificto particular embodiments. Certain features that are described in thisspecification in the context of separate embodiments can also beimplemented in combination in a single embodiment. Conversely, variousfeatures that are described in the context of a single embodiment canalso be implemented in multiple embodiments separately or in anysuitable sub combination. Moreover, although features may be describedabove as acting in certain combinations and even initially claimed assuch, one or more features from a claimed combination can in some casesbe excised from the combination, and the claimed combination may bedirected to a sub-combination or a variation of a sub combination.Similarly, while operations are depicted in the drawings in a particularorder, this should not be understood as requiting that such operationsbe performed in the particular order shown or in sequential order, orthat all illustrated operations be performed, to achieve desirableresults. Only a few examples and implementations are disclosed.Variations, modifications and enhancements to the described examples andimplementations and other implementations may be made based on what isdisclosed.

What is claimed is:
 1. An implant for shoulder arthroplasty, saidimplant comprising: a monolithically formed stem having a proximalportion, a distal portion, an anterior portion, a posterior portion, amedial portion, and a lateral portion, wherein the stem has a size andshape for insertion into an intramedullary canal of a humerus bone, thehumerus having a metaphysis and a diaphysis, wherein the proximalportion of the stem comprises a concave taper decreasing in size in adirection extending from the proximal portion toward the distal portion,and wherein distal portion comprises a distal taper decreasing in sizein a direction extending from the proximal portion toward the distalportion, and wherein the distal taper comprises a taper in a directionextending between the anterior portion and the posterior portion, andwherein the distal taper comprises a taper in a direction extendingbetween the medial portion and the lateral portion, and wherein theshape of the stem is configured to apply a first load to the metaphysisportion of the humerus bone and apply a second load to the diaphysisportion of the humerus bone, the first load being greater than thesecond load.
 2. The implant of claim 1, further comprising a lateralfin, an anterior fin, and a posterior fin, wherein the lateral finextends radially outward from the lateral portion of the stem, theanterior fin extends radially outward from the anterior portion of thestem, and the posterior fin extends radially outward from the posteriorportion of the stem, and wherein the lateral, anterior, and posteriorfins are configured to engage cancellous bone in the metaphysis orepiphysis to provide rotational stability to the stem.
 3. The implant ofclaim 1, wherein a lateral surface of the distal taper comprises aconvex curve extending in a direction from the proximal portion towardthe distal portion, and wherein a medial surface of the distal tapercomprises a concave curve extending in a direction from the proximalportion toward the distal portion, and wherein the taper in thedirection extending between the anterior portion and the posteriorportion is symmetric about a medial plane of the implant so as to allowbilateral usage in the shoulder.
 4. The implant of claim 3, wherein thetaper in the direction extending between the anterior portion and theposterior portion has a width, the width substantially equal to adiameter at a distal end of the concave taper on the proximal portion ofthe stem.
 5. The implant of claim 3, wherein the implant comprises acylindrical extrusion disposed adjacent the proximal portion of thestem, and wherein a first point is disposed on an anterior portion ofcylindrical extrusion and a second point is disposed on a posteriorportion of the cylindrical extrusion, and wherein a third point isdisposed distally away from the first point and the third point isdisposed on an anterior portion of the distal taper, and wherein afourth point is disposed distally away from the second point and thefourth point is disposed on a posterior portion of the distal taper, andwherein the first, second, third, and fourth points define a first totalincluded angle of a proximal portion of the distal taper, and wherein afifth point is disposed at a distal end of the stem and disposed on theanterior portion of the stem, and wherein a sixth point is disposed atthe distal end of the stem and disposed on the posterior portion ofstem, and wherein the third, fourth, fifth, and sixth points define asecond total included angle of a distal portion of the distal taper, andwherein the second total included angle is less than the first totalincluded angle.
 6. The implant of claim 1, wherein a distal portion ofthe stem comprises an hourglass shaped cross-section with a widthextending in a direction from the anterior portion toward the posteriorportion that is greater than a width at the medial portion or a width atthe lateral portion.
 7. The implant of claim 1, wherein a distal portionof the stem comprises a cutout section extending through the stem in adirection from the anterior portion toward the posterior portion, andwherein the cutout comprises medial and lateral edges which are offsetfrom a medial surface and a lateral surface of the stem, and wherein thecutout is configured to carry bone graft material.
 8. The implant ofclaim 1, wherein the proximal portion of the stem comprises rim, andwherein the rim comprises one or more protrusions extending outwardtherefrom, the one or more protrusions configured to be received into acorresponding receptacle in an articular cup or a head component.
 9. Theimplant of claim 1, further comprising a collar element disposedcircumferentially around the proximal portion of the stem.
 10. Theimplant of claim 1, further comprising one or more fenestrationsdisposed in the proximal portion of the stem, the one or morefenestrations extending in a direction from the proximal portion towardthe distal portion, wherein the one or more fenestrations are sized toallow a surgical instrument to pass therethrough.
 11. A system forshoulder arthroplasty, said system comprising: the implant of claim 1;and an articular cup coupled to the stem.
 12. The system of claim 11,wherein the articular cup is coupled directly to the stem.
 13. A systemfor shoulder arthroplasty, said system comprising: the implant of claim1; and a head component coupled to the stem.
 14. The implant of claim 1,further comprising a tapered receptacle disposed in the proximal portionof the stem, the tapered receptacle configured to receive a cooperatingtapered protrusion disposed on an articular cup or disposed on a headcomponent.
 15. The implant of claim 1, wherein the tapered protrusionhas length sized to permit use in anatomic or reverse arthroplasty, andwherein the tapered protrusion extends through the tapered receptaclethereby permitting an anatomic head component to be used the stem. 16.The implant of claim 1, further comprising a coating disposed over atleast a portion of the stem, the coating configured to promote boneingrowth into the stem.
 17. An orthopedic system for shoulderarthroplasty, the system comprising: an implant including a stem havinga proximal portion, a distal portion, an anterior portion, a posteriorportion, a medial portion, and a lateral portion, wherein the stem has asize and shape for insertion into an intramedullary canal of a humerusbone, the humerus having a metaphysis and a diaphysis, the stem beingarranged and configured for use in either of anatomic or reversearthroplasty; an articular cup arranged and configured to be coupled tothe stem; and a head component arranged and configured to be coupled tothe stem; the implant further comprising: wherein the proximal portionof the stem comprises a concave taper decreasing in size in a directionextending from the proximal portion toward the distal portion, andwherein distal portion comprises a distal taper decreasing in size in adirection extending from the proximal portion toward the distal portion,and wherein the distal taper comprises a taper in a direction extendingbetween the anterior portion and the posterior portion, and wherein thedistal taper comprises a taper in a direction extending between themedial portion and the lateral portion, and wherein the shape of thestem is configured to apply a first load to the metaphysis portion ofthe humerus bone and apply a second load to the diaphysis portion of thehumerus bone, the first load being greater than the second.
 18. Thesystem of claim 17, wherein the stem further comprises a taperedreceptacle disposed in the proximal portion of the stem, the taperedreceptacle configured to receive a cooperating tapered protrusiondisposed on the articular cup or disposed on the head component.
 19. Thesystem of claim 17, wherein the stem is monolithically formed.